1. Field of the Invention
The present invention relates generally to a visual travel route indicating apparatus for a vehicle. More particularly, the invention relates to a visual travel route indicating apparatus for use in an automotive vehicle or the like which is specifically designed to visually display combined information relating to a current status of travel of the vehicle, such as location, path of travel, travel direction, etc.
2. Description of Relevant Art
In attempts to prevent the driver of an automotive vehicle or the like from losing his way while driving such as at night or in unfamiliar surroundings away from his desired route of travel, there have been developed a variety of devices specifically designed to indicate continuously or discretely a current position of the vehicle, or like information, by way of an indication panel or display screen including a related road map or the like disposed at the driver's seat to provide ready guidance relating to the vehicle's current status of travel with respect to a desired course of travel.
Conventional travel route indicating devices for application as described above are constructed to operate in such a manner that a current travel distance of a vehicle is detected in accordance with its travel speed and time by a distance detecting unit. A current bearing or extent of azimuthal deviation of the vehicle is detected by a rate type bearing detecting unit adapted to detect a possible angular velocity as may be produced about the axis of yawing of the vehicle during a turning operation, and a current location of the vehicle along its travel route is obtained from an arithmetic operation performed on the thus-detected data as to the location of the vehicle. The thus-obtained results are indicated by way of spot information varying from time to time on a display unit which visually indicates a suitable road map of routes or roads on which the vehicle is to travel.
With the conventional arrangement as described above, it may be contemplated that a gas rate sensor be incorporated as means for detecting a current bearing of the vehicle by virtue of advantages afforded thereby. Such advantages include a substantial resistance against physical vibrations, a substantial sensitivity and a rapid response in comparison with a mechanical detecting device such as a gyroscope or the like. However, because such particular gas rate sensor is designed for detecting a possible angular velocity of the vehicle during a turning operation (if any) by detecting a fractional amount of change in a heat to be sensed by a gas flow sensor, which occurs in accordance with a current change in gas flow within the sensor from such an azimuthal change in motion of the vehicle, a current fluctuation in ambient temperature would unavoidably cause an immediate substantial disturbance to the sensor. Therefore, it is normally disadvantageous and impractical to incorporate a gas rate sensor of the aforesaid type, which is substantially susceptible to temperature fluctuations when employed in an automotive vehicle or the like where there would normally be a relatively high tendency toward such temperature fluctuations.
The present invention overcomes the aforesaid inconveniences and disadvantages attendant conventional travel route indicating apparatus specifically designed to detect and display the azimuthal change or angular velocity as produced about the axis of yawing of the automotive vehicle or the like by way of a gas rate sensor, which apparatus have not provided satisfactory results in operation.